* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Arial', sans-serif;
}

/* 页面容器：居中布局 */
body {
    min-height: 100vh;
    background-color: #f5f7fa;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: 20px;
}

/* 按钮样式：带 hover 交互 */
button {
    padding: 12px 24px;
    margin: 0 10px 20px;
    border: none;
    border-radius: 8px;
    font-size: 16px;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.3s ease;
}

/* 加法按钮配色 */
#addBtn {
    background-color: #4285f4;
    color: white;
}

#addBtn:hover {
    background-color: #3367d6;
    transform: translateY(-2px);
    box-shadow: 0 4px 8px rgba(66, 133, 244, 0.3);
}

/* 减法按钮配色 */
#subBtn {
    background-color: #ea4335;
    color: white;
}

#subBtn:hover {
    background-color: #d33222;
    transform: translateY(-2px);
    box-shadow: 0 4px 8px rgba(234, 67, 53, 0.3);
}

/* 结果展示区样式 */
#result {
    font-size: 18px;
    color: #2d3748;
    padding: 16px 32px;
    background-color: white;
    border-radius: 8px;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
    min-width: 200px;
    text-align: center;
}